Thomas Jefferson Papers

Notes on Pisé Walls, 16 October 1808

16-26 Oct. 1808

Pisé walls. Cointeraux’s new method of 1808.

a beam of timber 12. I. wide, 8¾ I. deep has mortises dug through it 8 I. wide & 14. I. long. this mould-beam is supported on benches with a thick plank (say 2. I.) under it, forming a bottom from which it can be easily hoisted. into the mould-mortise drop a board 14 I. by 8 I. scrimp & ¾ I. thick. put into the trough thus closed at bottom as much fresh earth just dug from the bank as, when beaten, will fill one third of the depth. over this drop in a block of 14. 8. & 6. I. and beat that with a sledge hammer or heavy mall until the earth below it shall be made perfectly solid. take out the block, scratch & peck the surface of the earth which will be found highly polished, & lay in another third of earth & beat that as before, & the same with the last third. the Moelon or fresh brick thus moulded, is disengaged by raising the mould-beam, & is taken up on it’s bottom board and deposited immediately on the wall with a thin joint of mortar as a cement. the size of 14. 8. & 8. is for a 14 I. wall, but certainly should be 14. 7. & of any height you please that you may lay a course of headers on a course of stretchers, breaking joints. for a 12 I. wall the moelons should be 12. & 6 &c

a moelon 14. 8 & 7½ French is [h][. . .] a cubic foot & will weigh 50. or 60. ℔ as much as a man can handle. most of the earths will do. those which form hard clods prove thereby their tenacity. vegetable soil having much glutens are good. so are clays, but unless mixed with other earth they are apt to crack. some sand improves the earth; if the earth is too dry it must be moistened with a [watering] pot. throw your earth into a conical pile from the spade that the stones & course lumps may roll to the bottom & get out of the way. lumps of the size of a hardnut or chesnut need not be reduced, the hammering will reduce them. the moisture should be about the degree of that of fresh earth dug out of a cellar. if too moist it will never compress.

DLC: Papers of Thomas Jefferson.

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